1. Field of the Invention
The present invention relates to a method for detecting an alignment mark for performing alignment, suitable for use in an exposure device or the like in producing semiconductor devices or the like.
2. Description of the Related Art
In producing semiconductor devices or the like, the most commonly used type of exposure devices utilize visible light or ultraviolet light in order to transfer a mask or reticle circuit pattern onto a wafer. With more advanced micromachining techniques of forming semiconductor circuit patterns, however, almost no further resolution can be provided, when visible or ultraviolet light is used to expose a pattern of the smallest size. Consequently, exposure using shorter wavelengths such as vacuum ultraviolet light or X-rays, or electron beams is drawing attention.
Putting such methods of exposure into practical use has the disadvantage that alignment of the mask and the wafer must be carried out with far greater precision than conventional alignments. In particular, when vacuum ultraviolet rays, X-rays, electron beams or the like are used, exposure must be carried out in a high vacuum, resulting in more severe conditions for alignment. At present, a method of exposure thought to be effective in detecting the position of an alignment mark is one using electron beams that provides high resolution. In general, however, multiple patterns are formed on the wafer by repeating the wafer forming process a plurality of times, causing the layer structure to change every time a cycle of the wafer forming process is repeated. Thus, an alignment mark, being detected using electron beams, is not necessarily detected under the same conditions, so that failure in the detection of an alignment mark may occur.
Accordingly, an object of the present invention is to provide a method or device that ensures precise detection of the position of an alignment mark, using electron beams.
Another object of the present invention is to provide an alignment method, an exposure method and device, and a device production method, using the alignment method.
To these ends, according to one aspect of the present invention, there is provided a method for detecting an alignment mark on a substrate, using electron beams, wherein an accelerating voltage of the electron beams is set in accordance with a layer structure of the substrate.
According to another aspect of the present invention, there is provided a method for detecting an alignment mark on a substrate, using electron beams, wherein the alignment mark is detected from fluorescent X-rays produced by illuminating the alignment mark by electron beams.
The present invention can also be carried out in the form of an alignment method, an exposure method, and a device production method, making use of either one of the aforementioned methods for detecting an alignment mark.
According to another aspect, the present invention which achieves these objectives relates to a method for detecting an alignment mark on a substrate using electron beams. The method comprises steps setting an accelerating voltage of the electron beams in accordance with a layer structure of the substrate, irradiating the substrate with the electron beams accelerated to the accelerating voltage set in the setting step, and detecting one of radiation and electron beams from the substrate after the irradiating step is performed and determining the position of the alignment mark based on the detecting.
According to still another aspect, the present invention which achieves these objectives relates to a method of detecting an alignment mark on a substrate using electron beams, comprising the steps of irradiating the substrate with electron beams, detecting fluorescent X-rays that are produced as a result of irradiating the substrate with electron beams in the irradiating step, and detecting the position of the substrate on the basis of the detected fluorescent X-rays.
According to still another aspect, the present invention which achieves these objectives relates to an alignment method for aligning a substrate having an alignment mark, comprising the step of setting an accelerating voltage of electron beams, irradiating the substrate with electron beams accelerated to the accelerating voltage set in the setting step, detecting one of radiation and electrons from the substrate after the irradiating step is performed, determining the position of the alignment mark based on the detecting performed in the detecting step, and aligning the substrate in accordance with the determining performed in the determining step.
According to still another aspect, the present invention which achieves these objectives relates to an exposing method for exposing a substrate to radiation projected through a circuit pattern in the mask to form the circuit pattern on the substrate. The method comprises the steps of setting an accelerating voltage of electron beams, irradiating the substrate with electron beams accelerated to the accelerating voltage set in the setting step, detecting one of radiation and electrons from the substrate after the irradiating step is performed, determining the position of the alignment mark based on the detecting performed in the detecting step, aligning the substrate with the mask in accordance with the determining method performed in the determining step, and projecting radiation through the circuit pattern of the mask to the substrate and forming the circuit pattern of the substrate.
According to still another aspect, the present invention which achieves these objectives relates to a device production method for producing a device, comprising the steps of setting an accelerating voltage of electron beams, irradiating the substrate with electron beams accelerated to the accelerating voltage set in the setting step, detecting one of radiation and electrons from the substrate after the irradiating step is performed, determining the position of an alignment mark on the substrate based on the detecting performed in the detecting step, aligning the substrate with a mask in accordance with the determining performed in the determining step, projecting radiation through a circuit pattern of the mask to the wafer and forming the circuit pattern on the wafer, and forming the substrate into a semiconductor device by repeating the projecting and forming step a plurality of times and repeating the irradiating, detecting, determining, and aligning steps each time the projecting step is performed.
According to still another aspect, the present invention which achieves these objectives relates to an apparatus for detecting an alignment mark on a substrate using electron beams, comprising means for setting an accelerating voltage of the electron beams in accordance with the layer structure of the substrate, means for irradiating the substrate with electron beams accelerated to the accelerating voltage set by the setting means, and means for detecting one of radiation and electrons from the substrate after the substrate is irradiated by the irradiating means and for determining the position of the alignment mark based on the detecting.
According to still another aspect, the present invention relates to an apparatus for detecting an alignment mark on a substrate using electron beams comprising means for irradiating the substrate with electron beams, means for detecting fluorescent X-rays that are produced as a result of irradiating the substrate with electron beams by the irradiating means, and means for detecting the position of the substrate on the basis of the detected fluorescent X-rays by the detecting means.
These and other objectives, features, and advantages of the present invention in addition to those discussed above will become more apparent from the following detailed description of preferred embodiment taken in conjunction with the accompanying drawings.